This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A131482 #42 Mar 23 2023 16:45:04 %S A131482 1,1,2,4,11,27,83,255,847,2829,9734,33724,118245,416816,1478602, %T A131482 5267171,18840144,67611472,243378415,878407170,3178068821,11523323634, %U A131482 41865833602,152382134767 %N A131482 a(n) is the number of n-celled polyominoes with perimeter 2n+2. %C A131482 2n+2 is the maximal perimeter of an n-celled polyomino. a(n) is the number of n-celled polyominoes that have a tree as their connectedness graph (vertices of this graph correspond to cells and two vertices are connected if the corresponding cells have a common edge). %H A131482 Andrew Clarke, <a href="http://www.recmath.com/PolyPages/PolyPages/index.htm?Isopolyos.html">Isoperimetrical Polyominoes</a>, The Poly Pages. %H A131482 Herman Tulleken, <a href="https://www.researchgate.net/publication/333296614_Polyominoes">Polyominoes 2.2: How they fit together</a>, (2019). %F A131482 a(n) <= A000105(n), a(n) <= A057730(n+1). %F A131482 a(n) >= A000602(n) [see comment on edge graph trees]. - _R. J. Mathar_, Mar 08 2021 %Y A131482 Cf. A000105, A057730. Diagonal of A342243. %Y A131482 A359522 counts only polyominoes with holes. %Y A131482 A002013 counts only unbranched polyominoes. %Y A131482 A038142 is the analog for polyhexes. %K A131482 hard,more,nonn %O A131482 1,3 %A A131482 _Tanya Khovanova_, Jul 27 2007 %E A131482 a(14)-a(16) from _David Radcliffe_, Dec 25 2017 %E A131482 a(17) from _David Radcliffe_, Dec 26 2017 %E A131482 a(18)-a(24) from _John Mason_, Dec 11 2021